**1. Introduction**

190 Biogas

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Cheese whey is a by-product generated during cheese manufacturing. The disposal of whey is problematic because of its high COD (Chemical Oxygen Demand) (about 50,000 mg L-1 - 80,000 mg L-1), low solids content (5% DM), low bicarbonate alkalinity and its tendency to get acidified very rapidly (Aktaş et al., 2006; González Siso, 1996; Venetsaneas et al., 2009). In 2008, Poland produced almost 1123 thousand tonnes of whey (Agricultural Market Agency [ARR], 2009). Traditionally, cheese whey has been used to feed animals, but redistribution of whey to farmers is very expensive. Moreover, lactose intolerance of farm animals also limits the use of whey in feeding (de Glutz, 2009). Since large quantities of whey are produced (about 9 kg of whey in the production of 1 kg cheese) (Zafar & Owais, 2006), there is an increasing concern as how it can be efficiently and cost-efficiently processed without adversely effecting the environment.

Proteins from cheese whey have a high nutritional value. For this reason cheese manufacturers have explored the possibilities of valorisation of whey. They recover proteins by membrane ultrafiltration (UF) process (Silveira et al., 2005). This method of separation has the main advantage – in does not denature proteins, so they save their original nutritional value (de Glutz, 2009). The residual protein-free material is called whey permeate. Permeate streams have very high COD value (about 50,000 – 70,000 mg L-1) (own studies), which represents an important environmental problem, similarly to whey. The chemical and biological instability of the UF whey permeate resulting in difficulties and high cost in its transport and storage. Proper management of this liquid is important due to strict legislation and economic reasons. Because of those there is a strong need to efficiently treat UF whey permeate.

UF whey permeate is composed mainly of lactose. Lactose concentration is about 50,000 mg L-1, so more than 90% of COD is due to lactose (de Glutz, 2009). Moreover, valuable compounds (proteins, vitamins) can be found in its composition. Since UF whey permeate contains significant quantities of lactose, the way to use this waste product could be as a substrate for fermentation to produce biofuels.

Nowadays, the most widely produced biofuels are ethanol and biogas (methane). Alcohol fuels are produced by fermentation of sugars derived from corn, sugar beet, sugarcane,

Feasibility of Bioenergy Production from

content in biogas.

**2.1 Materials and methods** 

**2.1.1 Fermentation medium and experimental system** 

in the reactors was controlled at the level of 7.0 ±0.05 with 2 M NaOH.

Fig. 1. Schematic of the laboratory-scale anaerobic treatment system

Ultrafiltration Whey Permeate Using the UASB Reactors 193

booming. Advances in biotechnology, molecular science and microbiology contributed to enhancements in biogas yields production (more high tech resulting in over 70% plant efficiency), which led to the development of commercial biogas plants (Yadvika et al., 2004). As a result, biogas competes with petroleum-based fuels in terms of performance, cost, and additional benefits such as reducing GHG emissions. Currently Europe dominates in biogas production (Prochnow et al., 2009). Germany, the biogas market leader, runs about 5000 biogas plants in 2009, covering more than 1% of the electrical energy consumption from biogas (Meyer-Aurich et al., 2012). However, the trend in producing biogas is also catching

Innovations are still necessary to support research and development in the field of renewable energy. The main research area is closely related to renewable biomass feedstock. Consequently, the objectives of this work were: (1) to investigate anaerobic biogas potential from UF whey permeate, (2) to evaluate if steel elements could enhance the performance of UASB reactors treating UF whey permeate (COD removal efficiency, phosphorus removal), and (3) to study the influence of steel elements on the biogas production rate and methane

Two identical Plexiglas laboratory-scale UASB reactors (R0 and RFe) with a working volume of 2.05 L each, one packed with spiral elements made of steel wire with an iron content of 48% (Fig.1; Table 1), were run in parallel at a constant mesophilic temperature of 35ºC ± 1ºC throughout a 219-day period. Four running stages were identified in term of OLR applied (Table 1). The OLR was increased stepwise from the initial 2.0 kg COD m-3 d-1 to finally 12.0 kg m-3 d-1. The reactors were operated for 25 – 66 days to ensure the reactors reached steady states at each stages (the steady-state conditions were evidenced when the standard deviations of COD removal efficiencies were within 3%). After the steady-state conditions were achieved, the OLR was increased to the next level. HRT at all stages was 48 h. The pH

up fast in countries like Japan, Australia, New Zealand, USA, China and India.

potatoes, wheat, followed by distillation and drying. The production of bioethanol from corn or sugarcane is a mature technology. For example, in Brazil there are 448 bioethanol production units installed and according to a report of the Brazilian Ministry of Mines and Energy, ethanol production was 25 billion liters in 2008 (Soccol et al., 2010). Biogas is produced by anaerobic digestion of organic materials by anaerobic microorganisms. It can be used to produce thermal energy (heating), electricity, or if compressed – it can be used in vehicles. The current operation of biogas plants is relatively large in Europe, especially in Germany. According to Pöschl et al. (2010), the estimated biogas production potential in Germany is 417 PJ per year and 80% of which derived from agricultural resources, including farm waste (96.5 PJ per year), crop residues (13.7 PJ per year), and dedicated energy crops (236 PJ per year).

More recently, hydrogen is playing more important role as a fuel used for heating, lighting and as a motor fuel. The main advantage of hydrogen as a future alternative energy carrier is the absence of polluting emissions when combusted, results in pure water. Today, most hydrogen gas is obtained from fossil fuels which generate greenhouse gas (GHG) that contribute to global warming. The biological hydrogen production is an attractive method because it can be produced from renewable raw materials such as organic wastes. Wastewater from food processing industries show great potential for economical production of hydrogen (Van Ginkel et al., 2005), but today no strategies for industrial-scale productions have been found.

The ability to produce biofuels from low-cost biomass such as agricultural waste and byproducts (including for example crop residues, sugar cane waste, wood, grass and wastewater from food processing industries) will be the key to making them competitive with other fuels, for example gasoline. Only biofuels derived from waste products show low environmental effects, such as reduction of GHG emission, small land demand and damage the environment. As a result, since UF whey permeate disposal represent a real problem for the dairy industry, biofuels production offers an ideal alternative to its valorization (de Glutz, 2009; Silveira et al., 2005).

The objectives of this work were to study the applicability of fermentation processes for the production of biogas (methane), fuel bioethanol and biohydrogen in Upflow Anaerobic Sludge Blanket (UASB) reactors fed with raw UF whey permeate. To optimize and enhance the biofuels production, the different processes were used (ultrasonic stimulation of microbial cells, anaerobic steel corrosion process) and the different operational parameters (pH, hydraulic retention times - HRTs regimes, organic loading rates - OLRs) were applied.
